PDF forms contain an array of fields that are represented as individual controls or groups of controls on the pages of a PDF. You can iterate through this array and manipulate these controls to change their values.

All Acroforms-based access to the PDF fields is provided by the Fields property of an ImGearPDFDocument.Form. If a loaded PDF document has no form, the Form property will be null. Use CreateForm to create an empty form.

You can access fields though iteration or index-based access. Iteration is accomplished through an IEnumerable object; the indexed access provides two interfaces: by full name or by numerical field index. Once a Field object is obtained, see Read and Write Form Field Values to read values.

Iterating over Form Fields

Iteration over the Fields property can be done using a foreach loop, a for loop, or any method consuming an IEnumerable object. Fields returns the number of fields in the PDF form.

void IterateFormFields(ImGearPDFDocument pdf)
{
    if (pdf.Form == null)
    {
        pdf.CreateForm();
    }
    foreach (Field field in pdf.Form.Fields)
    {
        // Operate on the field here...
    }
    for (int i = 0; i != pdf.Form.Fields.Count; ++i)
    {
        // Operate on the field here...
    }
}

Index-based Traversal

Index-based traversal allows random access to fields. When indexing by name, the name is the full name of the field. A full name is a number of partial names separated by periods: see the FullName property for details. The numerical index order is the same as the iteration order, as mentioned above.

void ProcessFields(ImGearPDFDocument pdf)
{
    var name = pdf.Form.Fields[0];
    var address = pdf.Form.Fields["address.state.county"];
    // Operate on the fields here...
}